Warning, long post!

Freezing of the ballast tanks is not the only problem.

I am "closely familiar" with three separate water ballast incidents.

The first was in a 2 seat Schempp-Hirth glider with the type of tail ballast
tank that has holes that one tapes over to determine the ballast quantity.
Half way into a 300K out and return flight and after some straight cruising
at altitudes of 16-18K feet (4500-5500 meters) it was noticed that the
rudder would not move. Moderate pressure on front, back and both sets of
rudder pedals would not free the rudder in either direction. It was still
possible to soar the glider toward home and it was possible to thermal,
though without the use of the rudder it was not pretty. On final glide at
about 10K feet (3000 meters) the rudder came loose and the pilots made an
uneventful landing. Inspection of the rudder area showed that the tape,
which had been on the glider for some time, had pooched out and started
leaking from one of the lower holes. It appeared that the water had run
into the rudder counterweight slot and had frozen there. Landing without
rudder could have been ugly.

The second incident was on the same Schempp-Hirth 2 seat glider. The
ballast drains are some distance from the wing roots and draining is visible
to the front pilot while dumping the ballast. The glider was again being
flown long distances at high altitudes above the freezing level. The front
pilot noticed that there was a fin of ice extending below and aft of the
drain opening about 2" wide, 6" high (50 X 150mm) and extending to the
trailing edge of the wing. This appeared to not cause much degradation to
the handling or performance of the glider, and the fin fell off upon
descending through the freezing level. The valve was obviously leaking, not
enough Chap Stick on the valve!

The third occurrence was in a PIK-20D sailplane which had taken off with a
known slow drip coming out of the wing at the back of the right side wing to
fuselage tape. After a period of cruising at high altitude a thermal was
entered, a pull-up was initiated followed by increasing the flaps to the
thermalling setting. The stick was pushed to the right side by the flap
position change and an un-commanded and brisk aileron roll was started to
the opposite side from the left turn that was desired. The flaps were
promptly put back in the cruise setting and the glider was able to be
ruddered into the thermal from a right turn. It was determined that the
flaperon on the right side was stuck in position. Some judicious wiggling
of the stick was able to free the stuck flaperon and the flight continued
with regular wiggles of the ailerons. Conditions were very good on the
return and the speed on final glide was increased to 130 knots when BANG,
BANG, BANG was heard which was followed by a gentle pull up to a slower
speed. The noise soon went away and the glider was slowly speeded up again
which was OK. After landing it was noticed that the tape on the bottom of
the right wing was separated from the surfaces from the front of the flap
forward to half chord and was stretched to 12" (30 cm) behind the wing. The
problem was probably caused by a buildup of ice on the flaperon flow fence
below the wing which froze the flaperon in position and then, later, on
final glide, broke off and, stuck to the tape, was beating against the
fuselage like a mace.

Yes, the pilot involved in all these incidents knew about dumping ballast
passing the freezing level but figured that it would take a long time to
freeze the water in the tanks, which is true. Some guys just don't learn
with experience that there might be other problems. (-;

Y'all be careful out there...
-Bob Korves




"Bob Salvo" wrote in message
...
Then put the ballast temperature sensor in the tail tank, which should
also
be insulated to help prevent heat loss.

Bob

"Marc Ramsey" wrote in message
.. .
Bob Kuykendall wrote:
Has anybody on this forum ever, ever looked at the OAT guage and said,
hey, it's too cold here, I'd better dump water or descend?

Yes.

Given how effective composite sandwich construction can be as an
insulator, it seems to me that what they _should_ be requiring is a
ballast temperature guage...

The main problem is the tail tank, which is a relatively small volume of
water, isn't all that well insulated, and will freeze in a matter of a
few hours if the outside temperature is low enough. In at least one
case, the expansion of the ice caused the vertical fin to split open...

Marc